From 1d54cf2b973a6265789b382b7d305771321b9b57 Mon Sep 17 00:00:00 2001 From: "sukadev@linux.vnet.ibm.com" Date: Tue, 30 Aug 2011 09:19:17 +0000 Subject: powerpc: Implement CONFIG_STRICT_DEVMEM As described in the help text in the patch, this token restricts general access to /dev/mem as a way of increasing the security. Specifically, access to exclusive IOMEM and kernel RAM is denied unless CONFIG_STRICT_DEVMEM is set to 'n'. Implement the 'devmem_is_allowed()' interface for Powerpc. It will be called from range_is_allowed() when userpsace attempts to access /dev/mem. This patch is based on an earlier patch from Steve Best and with input from Paul Mackerras and Scott Wood. [BenH] Fixed a typo or two and removed the generic change which should be submitted as a separate patch Signed-off-by: Sukadev Bhattiprolu Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/mm/mem.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'arch/powerpc/mm/mem.c') diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 2dd6bdd31fe1..22563b9664c3 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -585,3 +585,21 @@ static int add_system_ram_resources(void) return 0; } subsys_initcall(add_system_ram_resources); + +#ifdef CONFIG_STRICT_DEVMEM +/* + * devmem_is_allowed(): check to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * Access has to be given to non-kernel-ram areas as well, these contain the + * PCI mmio resources as well as potential bios/acpi data regions. + */ +int devmem_is_allowed(unsigned long pfn) +{ + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +} +#endif /* CONFIG_STRICT_DEVMEM */ -- cgit v1.2.3